Automatic-slack-adjuster-for- brakes-



Feb. 7, 195 L. c. BRxssoN 2,733,781

AUTOMATIC SLACK ADJUSTER FOR BRAKES Filed Aug. l5. 1.952

United Stateszatent 21,733,181] AUTOMATIC -SLACIQ ./.ilrIUsrnnl lroR-'BRAKESh Louis;CharlesBISSOPVPQFE; EMM@ Application August 13, 19512,?A Serial'l No: 3Dfl1f78 Claimsartoria",v applicafianfFrance t August-.1?,- 191513 2Claim= (.CL; 15$.196)1 This invention relates to` brakes providedwithmeans; for automatically taking-up,theiweargof the lining,` of. the brake shoe, or shoes, and? particularly to; brakespro videdlwith an automaticdevice for, takingruphe; wear` of theY p typey comprisingy ar threaded; member. I actuated. by; a toothed gear` drivenaby, a mechanism'which-tadvances; it by one;tooth.at.each;applicationof;the; brake. TheJ inventionV liasl for itsf object an;I improved-wear, taking-,updevice of, this type.

In order to solve'practically, infaI satisfactoryv manner, the problem of:the;takingup.of the:wearpot brakeushoes, the' solution must meet thef following;y doublelicondition:

1'. It `must take up'the'play. corresponding'.to,,thefwearl ofzthe lining of; the. shoe-or: shoes;

2. It must not take up any play arising out 4ofi a; difference of expansion of` the brake shoe or shoes and of the brakedrum.'

A simple arrangement which gives very `good results is known, comprising an escapementdevice whichoperates as soon `as the play'tobe'taken:iip'rexceeds;a-A certain amount which is predetermined, theA play taken up'`v at eachescapement of the" device beingfiied and; ,srnallry A .l device ofgthis` kind is known,` comprising a, `tljrea'de:,d member controllingthe wear taking-up,"` actuated by' a toothed Wheel drivenv byanescapeirieiit mechanismwh'ich causes it to advance one. to'othiat .eachjs application of the brake, thereby advancing the ,threaded membenby ayery small fraction ofthepitch of the thread.

Such a device functions very well when the masses of the shoe or shoes and of the drum are moderate so that their temperature are quickly reduced to a negligible amount.

When these masses are important, however, as in the case of heavy-weight vehicles, such as device can no longer function satisfactorily, because the time required for the equalization, even only approximate, of the temperatures is very long and it is possible that there will be during this time, under certain driving conditions, a relatively large number of applications of the brake with consequential operation of the wear taking-up device each time, with the result that there will be an objectionable tightening of the brake shoe or shoes against the brake drum, after cooling of the whole, in the no-braking position.

The simplest way of improving the working of such an arrangement for taking-up the wear would be to decrease the amount of play taken up at each escapement of the mechanism; if, in fact, one could diminish it suflciently, one would ind oneself again dealing with the case of the brake shoe or shoes and brake drum of small masses.

Unfortunately, it is diicult to sufficiently diminish the pitch of the thread of the member which is generally used for taking up the play under control of the escapement device; an increase in the number of teeth of the escapement arrangement, whihe would have the desired eiect, would have to be considerable, in fact, much greater than is practicaly possible, to achieve a satis- 2 factory.` result'l Evenby using adiierentialL screwv arrangement',theresultingrpitch wouldbestill toolarge.

Accordingto the invention, toreme'dy these drawbacks, I provide anarrangement for taking-upthe wear ofthe liningiofA abra'le shoe orshoesof thev typerefer'red'to, characterised. by.v an mechanism adapted. tof renden the; escapement ofA a tooth of"A the toothedlgevar effective in actuatinglthe weartakiiigupf deviceonly once duringawhole revolutionpfithe -saiditoo'thed t gear.

Preferably, the member actuating fthe chain` ofj brakeshoes- Whenthe` brake;` istapplied is al threadedqsoclceti adapted to be rotatedlbyonelstepwhen tliees'capement=of a toothaofthe toothed-'gear aforesaid isrrendered' eec# tive by a ratchet-arrangementfwliich operates-onlyf onc'e for.v a *whole revolution otfthe saidto'othel gear, the said socketbmemberactuatingithe chain oftbrake shoes throughy the inte'rrrrediaryA of a@ threaded member screwed into Y the saidsocketiandprevented from rotating with the-latter,- so thatiitadvances longitudinally by avery smalll fraction` ofthe pitch of! the` threadi whenever thethreaded' socketi rotates by one step of the ratchet arrangement:-

Brefe'rably, thelfa'vctor.` which determines whetheri the escapement ofon'e tooth' of? the toothed gear aforesaid wilLy be eective-inrotatingthe threaded socketbyonef step is a` spring? controlled iingermountedlon th'eltoothedl gea-r, broughtinzoperation-rbyfa camLsurfa'ce-onthe Xedsupport ofithe4 wholedevice and@ engaging'- oneof theteeth' of-a ratchet wheelsolid with the threaded socket.

t Other cl'ia'racteristic':l featuresl andl advantages ofy the? prese-nty inventionawill appear. during-the descrip-tion which i followsg withf reference toc the Aaccompanying drawing onl whichi is representedldiagramiriaticallyand inl the wayot? example; only-` a preferredlembodirnent of the invention.`

In-tliisdrawing:V V

Figt 'l is a longitudinal, `axial section ofi the device-ac-y cordingto/theinve'ntiongYv Fig. 2 is a transverse section-alongIe-II of-"Figf 1;'

Fig; 3 @is-1a view-of-:detailg being 1 al partial section along ini-1u ofz'Fig. 1; y

In the iigure's,=1 isa threaded :member screwed intolan internalyf threaded@ socketi.v 2-1 and@ prevented.r froms turn-s ingr witlithesaid socket? bya anyY suitable means sucht as'- a device which cangfforV instance; be-similar ot that-ishow'n. in Figure 2 of my previous U. S. Patent No. 2,131,369, the head of said threaded member being provided with a slot 1a in which a part of the adjacent shoe can be inserted. The socket 2 and member l constitute an intermediate member between the chain of brake shoes (not shown) in the one hand, and the controlling member 3, on the other hand, this controlling member being actuated by the operator through an arrangement for brake control of any known type, whether it be mechanical, pneumatic or hydraulic.

Around the socket 2 is mounted rotativeiy a disc member 4 on which are disposed the teeth 5 of the toothed crown of the escapement device, adapted to be engaged by a pawl 8 pivoted at 9 on the Xed support liti of the mechanism, under the thrust of a spring 11 housed in the said support. This disc member s is heid between a flange 6 of the socket and a maintaining washer 7, so that it is carried along in translation with the controlling member 3, on which the socket is rotatively mounted, While this disc member 4 can turn with respect to the socket 2. It will be seen that, when an application of the brake takes place, the controlling member 3 descends and, with it, the whole mechanism constituted by the socket 2, disc member 4 and threaded member l., while the paw! 8 remains in position on the support 16, momentarily out of engagement with the toothed crown 5.

ln accordance with the invention, the socket 2 is provided with a groove 12 provided with circumferential ratchet teeth (Fig. 2) adapted to be engaged by the chamfered end of a finger 13 slidably mounted in a bore in the disc member 4. When the other end of this iinger, which bears against the internal surface 14 of the support 10, passes over a boss 15 on this surface, the finger is pushed into engagement with the ratchet teeth 12 against the Vthrust of a spring 16, which normally maintains it out of engagement with these teeth when the boss 15 is in another position.

In operation, when braking, the member 3 is displaced downwards (Fig. 1) under the action of the operating device of the brake, carrying with it the socket 2 and the member 1. The socket 2, in its turn, carries down the disc member 4, thereby moving the toothed crown 5 away from the pawl S, as explained above. When the brake pedal is released, the whole returns into the position shown in Fig. l and the toothed crown returns in engagement with the pawl 8, which causes the disc member 4 to turn through an angle corresponding to one tooth.

Should the boss happen to be in any position such as that shown in Fig. 2, in which it does not push the inger 13 in engagement with the ratchet teeth 12, this rotation of the disc member 4 does not entail any rotative movement of the socket 2 and, consequently, no movement of the member 1 in the direction of the taking-up of the play.

When a certain number of applications of the brake have been efected, the member 4 having each time` turned through an angle corresponding to one tooth, as it has been explained above, there comes a moment (once in each rotation of this member 4) when the boss 15 comes under the head of the finger 13, which is then pushed in engagement with the teeth 12 on the socket 2, thereby rendering the member 4 solid with the socket 2; the latter, consequently, is carried along with the rotation of the member 4 and this causes a relative motion of the member 1 with respect to the socket 2, resulting in a taking-up of the play. This only takes place once during a complete rotation of the member 4, instead of Vat every application of the brake, as is the case with the brakes in use at the present time, with the drawbacks which have been explained.

It is seen that, in this manner, one carries into effect, in a very simple manner, an arrangement which permits to take up the wear of the lining of the shoes, without this taking up of the play being excessive and producing an objectionable tightening of the brake shoes against the brake drum in the non-braking position.

What I claim is:

1. In a device for taking-up the wear of brake shoes, a controlling member for said brake shoes, a xed support for said controlling member in which said controlling member is movable, an internally threaded socket rotatively mounted on said controlling member, a threaded member cooperating with said internally threaded socket, one end of said threaded member being engaged in said socket and the other end beingV arranged so as to be connected to one of said shoes in a fixed angular relationship with respect thereto, a disc member rotatively mounted on said socket, a crown of teeth on said disc member, means for causing said dise member to advance one tooth of said toothed crown at every application of the brake beyond a predetermined travel of said controlling member and means for locking said disc member to said socket once in every revolution of said disc member.

2. A device as claimed in claim l, wherein said means for locking said disc member to said socket once in every revolution of said disc memberV comprise a cylindrical housing for said device in said xed support, a ring of ratchet teeth on the said socket, a spring actuated nger housed in said disc member, one end of said spring actuated iinger engaging the teeth of said ratchet, the other end of' said spring actuated finger controllably bearing against the internal cylindrical wall of the housing in said Xed support,.and a cam surface on said internal cylindrical Wall for moving the end of said finger and to push it into engagement with the teeth of the ratchet, thereby locking the said ratchet with the disc member at least once in each complete revolution of the latter to cause the said socket to be moved by the ratchet when advancing one tooth.

References Cited in the tile of this patent UNITED STATES PATENTS 1,875,065 Lyman Aug. 30, 1932 1,971,643 De Lavaud Aug. 28, 1934 1,998,533 Brisson Apr. 23, 1935 2,077,940 La Fitte Apr. 2.0, 1937 2,131,369 Brisson Sept. 27, 1938 2,152,041 Goepfrich Mar. 28, 1939 FOREIGN PATENTS 525,487 Great Britain Aug. 29, 1940 

